Ian McEwan is one of a number of contemporary British writers who believe they have a responsibility to draw attention to the moral shortcomings of domestic and international politics, particularly the social policies of Margaret Thatcher and the foreign policy of the United States. They include John Mortimer, Martin Amis, Salman Rushdie, Margaret Drabble, David Hare, Hanif Kureishi, Fay Weldon, Adam Mars-Jones, Jeanette Winterson, and Ben Elton, and their leader, though neither he nor they would ever dream of describing him as such, is Harold Pinter. They are, with justification, some of the most widely disliked people in Britain.

It is important to get clear what it is that makes them so objectionable. For instance, it isn't that, as beneficiaries of Conservative fiscal policy and American military protection, they aren't entitled to criticise them. Mrs Thatcher and a number of her cabinet colleagues are beneficiaries of the social reforms carried out by the 1945-51 Labour governments yet no one suggests that this prohibits them from criticising the welfare state. Nor is it that, as writers, they are somehow overstepping their brief or transgressing some sacred line. Some of the most clear-sighted political commentators, such as Benjamin Disraeli and George Orwell, have also been writers of fiction.

What rankles is the suggestion that it is in virtue of their craft that writers like John Mortimer and Margaret Drabble possess some special insight into contemporary politics which is denied to the rest of us. Because of their imaginative powers and heightened sensitivity, they are uniquely qualified to estimate the true worth of our society. Martin Amis has described the novelist's subject-matter as "the cabbalistic signs of modern life", implying that writers can see things which are hidden to others. They are blessed with an 'inner ear' which is perfectly attuned to the pulse of our times; the zeitgeist reveals itself exclusively to them.

This belief is clearly just a form of fantastic professional vanity, 'writers' possessing no more moral intelligence in virtue of their vocation than, say, dustmen or traffic wardens. But what makes this particular form of self-aggrandizement so hard to stomach is that it is packaged in the language of humility. Thus, it is because they possess no illusions about their own frailty and vulnerability that 'writers' are able to take the true measure of things like nuclear weapons; because they don't suffer from the egotistic need to impose themselves on the world it reveals itself to them as it really is. And all the while they are promoting themselves as some kind of secular priesthood.

Ian McEwan first made a bid to join this club with his screenplay for The Ploughman's Lunch, Richard Eyre's 1983 film depicting the moral bankruptcy of the Eighties through the eyes of a cynical, self-seeking hack. This was followed by A Child In Time which contains some embarassing stabs at political satire, such as having a Conservative government privatize beggars. A Child In Time won the 1987 Whitbread Novel of the Year award, but true recognition came in June of that year when the Pinters and the Mortimers invited McEwan to join The 20th June Group, the writers' think tank set up to discuss ways of combatting Thatcherism.

The Innocent marks McEwan's entrance into the international arena: having done Thatcher's Britain he now takes on the Cold War. It is set in Berlin in 1955 and documents the professional and personal awakening of Leonard Marnham, a 25-year-old electronics engineer from Tottenham. Leonard is in Berlin to work on Operation Gold, an Anglo-American intelligence project to tap Soviet phone lines by tunnelling into the Russian sector. Initially, he is only trusted with unpacking tape recorders, but he soon receives level four security clearance and is recruited by John MacNamee, a British government scientist, to spy on the Americans. Meanwhile he is picked up by Maria Louise Eckdorf, a beautiful thirty-year-old German woman, who initiates him into some of Berlin's other secrets. Before long, the shy, bespectacled hero is completely out of his depth, mixed up in murder, espionage and betrayal.

The novel works best on the level of a well-researched historical thriller. McEwan's evocation of post-war Berlin has the smack of authenticity and his fictional narrative is nicely intercut with actual historical events: Operation Gold really did take place and there is even a cameo appearance by George Blake. The atmosphere of impeding catastrophe is well constructed and the climax, in which Leonard frantically tries to dispose of a corpse, is genuinely exciting. However, McEwan is much more ambitious than this and The Innocent is clearly trying to tackle some much bigger issues than the average Len Deighton. As the novel progresses it becomes increasingly clear that Leonard and Maria's relationship is intended as nothing less than an allegory of the Cold War itself.

For instance, Leonard and Maria can be seen as representatives of their respective countries, the tension between them signifying the tension in Anglo-German relations. Thus, their relationship almost founders when Leonard begins to perceive her as the defeated German nation:

He looked down at Maria, whose eyes were closed, and remembered she was a German. The word had not been entirely prised loose of its associations after all. His first day in Berlin came back to him. German. Enemy. Mortal enemy. Defeated enemy. This last brought with it a shocking thrill. He diverted himself momentarily with the calculation of the total impedance of a certain circuit. Then: she was the defeated, she was his by right, by conquest, by right of unimaginable violence and heroism and sacrifice. What elation!

More significantly still, Leonard and Maria are manipulated by Bob Glass, a brash American intelligence officer. In fact, when they eventually do split up it is largely because Maria cannot reveal to Leonard that she has told Glass a secret about their relationship since to do so she would have to reveal that Glass had told her a secret about Leonard. Surely a moral here about the adverse effect of secrecy on international relations.

This motif is pushed to ridiculous extremes in the centre-piece of the novel in which Leonard and Maria have to dispose of the corpse of Otto, Maria's ex-husband, whom they have just killed. They decide the best thing to do is to cut Otto into small pieces and pack him into two suitcases. There follow ten, gruesome pages in which Otto's dismemberment is described in language reminiscent of H.P. Lovecraft. McEwan goes to some lengths to make Leonard and Maria's decision seem plausible under the circumstances, but clearly his real reason for including this scene is its allegorical significance. The chopping up of Otto's corpse is obviously intended to parallel the partition of Berlin after the Second World War.

The central point of The Innocent, then, is that the very same forces which can destroy private relationships - jealousy, suspicion, violence, secrecy - can destroy the relations between states. The division of Europe is due to nothing more than failing to keep a close enough eye on the same dark forces which disrupt our personal lives. Thus, our politics are diseased, but not - as the hint of reconciliation between Leonard and Maria in the final part of the book set in 1987 implies - incurably so.

The trouble with this thesis is that it depends on drawing an analogy between the private and the public, the personal and the political. The central conceit of McEwan, Pinter, Drabble, et al, is that a thorough understanding of private life will enable you to understand public life. It is this which makes 'writers' so well-qualified to comment on political matters. But to imagine that political conflicts hinge on exactly the same fulcrum as personal ones is obviously a vast oversimplification; the political just isn't that personal. There are, for instance, such things as genuine, deep-seated, highly complex ideological differences which do not effect private relationships but are absolutely central to politics. Consequently, it is doubtful that a writer like Ian McEwan will be able to say anything interesting about the Cold War until he acquaints himself with these differences.

Of course, there is nothing in principle to prevent McEwan and his fellow political authors from saying anything interesting about these issues, though it will require an expertese which they currently don't possess. What is pure poppycock is the suggestion that, in virtue of their being writers, they already possess an expertese in these areas which the rest of us cannot even approach. And it is poppycock of an acutely irritating kind.